duplocale(3) Linux Man Page

Name

duplocale - duplicate a locale object

Library

Standard C library ( libc ", " -lc )

Synopsis

#include <locale.h> 
locale_t duplocale(locale_t  locobj );

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

duplocale()

    Since glibc 2.10:
        _XOPEN_SOURCE >= 700
    Before glibc 2.10:
        _GNU_SOURCE

Description

The duplocale() function creates a duplicate of the locale object referred to by locobj.

If locobj is LC_GLOBAL_LOCALE ,duplocale() creates a locale object containing a copy of the global locale determined by setlocale(3).

Return Value

On success, duplocale() returns a handle for the new locale object. On error, it returns "(locale_t)\ 0", and sets errno to indicate the error.

Errors

ENOMEM Insufficient memory to create the duplicate locale object.

Standards

POSIX.1-2008.

History

glibc 2.3.

Notes

Duplicating a locale can serve the following purposes:

To create a copy of a locale object in which one of more categories are to be modified (using newlocale(3)).

To obtain a handle for the current locale which can used in other functions that employ a locale handle, such as toupper_l(3). This is done by applying duplocale() to the value returned by the following call:

loc = uselocale((locale_t) 0);

This technique is necessary, because the above uselocale(3) call may return the value LC_GLOBAL_LOCALE ,which results in undefined behavior if passed to functions such as toupper_l(3). Calling duplocale() can be used to ensure that the LC_GLOBAL_LOCALE value is converted into a usable locale object. See EXAMPLES, below.

Each locale object created by duplocale() should be deallocated using (3)freelocale .

Examples

The program below uses uselocale(3) and duplocale() to obtain a handle for the current locale which is then passed to toupper_l(3). The program takes one command-line argument, a string of characters that is converted to uppercase and displayed on standard output. An example of its use is the following:

$ ./a.out abc
ABC

Program Source

#define _XOPEN_SOURCE 700
#include <ctype.h>
#include <locale.h>
#include <stdio.h>
#include <stdlib.h>

#define errExit(msg)    do { perror(msg); exit(EXIT_FAILURE); \e
                        } while (0)

int
main(int argc, char *argv[])
{
    locale_t loc, nloc;

    if (argc != 2) {
        fprintf(stderr, "Usage: %s string\en", argv[0]);
        exit(EXIT_FAILURE);
    }

    /* This sequence is necessary, because uselocale() might return
       the value LC_GLOBAL_LOCALE, which can't be passed as an
       argument to toupper_l(). */

    loc = uselocale((locale_t) 0);
    if (loc == (locale_t) 0)
        errExit("uselocale");

    nloc = duplocale(loc);
    if (nloc == (locale_t) 0)
        errExit("duplocale");

    for (char *p = argv[1]; *p; p++)
        putchar(toupper_l(*p, nloc));

    printf("\en");

    freelocale(nloc);

    exit(EXIT_SUCCESS);
}

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